The invention relates to a method of producing a part from cast and worked titanium alloy and intended for example for compressor discs for aircraft propulsion system, and also to the parts obtained;
In their patent EP-B-0287486=U.S. Pat. No. 4,854,977=U.S. Pat. No. 4,878,966, the Applicants described a method of producing a part from titanium alloy having the following composition (% by mass): Al 3.8 to 5.4--Sn 1.5 to 2.5--Zr 2.8 to 4.8--Mo 1.5 to 4.5--Cr less than or equal to 2.5 and Cr+V=1.5 to 4.5--Fe&gt;2.0--Si&gt;0.3--O.sub.2 &lt;0.15 and Ti and impurities: the balance. According to this process, an ingot of the said alloy is hot worked this hot working comprising a roughing down under heat giving giving a hot blank, then final working of at least a part of this blank preceded by preheating to a temperature situated above the real beta transus of the said hot rolled alloy, the ratio of this final rolling "S:s" (initial cross-sectional:final cross-section) preferably being greater than or equal to 2, after which the part blank obtained by this final working is subjected to a solution heat treatment, and then an ageing treatment. The parts obtained have an ex-beta acicular structure with alpha phase at grain boundaries. The best set of mechanical characteristics obtained thus (sample "FB", tests according to the direction L) is: Rm=1297 MPa--R.sub.p0.2 =1206 MPa--A %=6.9--K.sub.1c =51 MPa..sqroot.m. Creep at 400.degree. C. under 600 MPa: 0.2% in 48.5 hr and 0.5% in 384 hr. in terms of service life, it has been found important to improve if possible the ductility (A %) without reducing the other mechanical characteristics.
The Applicants have sought to achieve this improvement and more generally to improve the compromise of mechanical properties obtained in such a titanium alloy component.